C5 Knocking When Cold + Crankshaft Pulley

[qman3428]

Have to say my 2009 2.0 exclusive sounds the same. 120k on the clock and goes like a train. I dont think you have anything to worry about.

[Howiec]

Thanks Qman,   that's put my mind at rest.  Cheers Howard.

[FridgemagnetC5]

I had this issue with a failing crankshaft pulley on my old 2.0 HDI. It took a long time (about 30,000 miles) to go from the initial slight rattle to what sounded like a terminal tappet death rattle, but it finally revealed itself by the pulley spitting bits of shredded spring everywhere. Some tips:

 

• Switching the aircon on makes the noise worse as the compressor loads the pulley more.
• The crankshaft bolt took ages to get out as the friction of unscrewing made it heat up, swell and jam. I had to loosen it by a quarter turn and leave it to cool for a couple of minutes. Repeat for about an hour - it's a long bolt!
• There's a freewheeling clutch mechanism on the alternator pulley. If this is jammed solid (as mine was) then lifting off the throttle sends excessive forces down the auxilliary belt to the crankshaft pulley, accelerating the wear and tear.

I replaced the pulley with an OEM spec, and replaced the alternator with one that didn't have a seized clutch. It was all still good 100k miles later.

[paul.h]

Welcome to the forum and thanks for the info. There is a special procedure for the crankshaft bolt which seems to involve slackening and tightening to get it undone:

 

The crankshaft pulley bolt has on its thread an adhesive which activates on tightening. This adhesive makes the assembly of the crankshaft belt drive pulleys safe.

On slackening, particles of adhesive could possibly accumulate in significant quantities in the threads, thus rendering the operation particularly difficult and also possibly leading to the bolt breaking inside the crankshaft.

It is important to keep to the slackening procedure so that the operation will succeed.

 

3. Slackening procedure

CAUTION : Use of an impact wrench is prohibited : Risk of the bolt breaking inside the crankshaft.

CAUTION : Keep to the method "Removing - refitting : Associated timing belt".

 

3.1. Slackening at the correct torque

CAUTION : The flywheel immobilisation tool must be in place.

Slacken the bolt using a wrench (Do not exceed 1 turn).

CAUTION : During the slackening, make sure that the resisting torque does not exceed 200 Nm; By using a reversible torque spanner.

Slackening the bolt :

• Unscrew the bolt ; Monitor the resisting torque
• If the effort increases, redo up and then renew the slackening (More than once if necessary)
• Alternately repeat the above operations until the bolt is completely slackened

N.B. : As the slackening effort increases, it is important to retighten fully so as to spread the adhesive which has accumulated in the threads.

CAUTION : Stop the operation if the slackening effort is too great (greater than 200 Nm). Go to the next section.

 

3.2. Slackening with heating of the bolt

CAUTION : The heat of the gun can damage the rubber sealing on the ancillary drive pulley. Do not exceed 4 minutes of heating.

Heat the head of the bolt for 4 minutes ; Using a hot air gun fitted with a small calibre adaptor.

CAUTION : Monitor the slackening torque, using the torque spanner, do not exceed 200 Nm.

Undo the bolt immediately.

Repeat the operation for 1 minute if the slackening effort still remains too great.

 

4. Checked - Cleaning

CAUTION : Check the state of the rubber sealing on the ancillary drive pulley. Check the state of the target of the engine speed sensor. Replace parts that are damaged.

Always replace the bolt if the slackening torque reached 200 Nm.

Clean (M14 x 150 tap) :

• The thread
• The tap

[RichCliff]

I've just had my engine knocking (for over a year) repaired and it turned out to be the auxiliary belt pulley/tensioner which was the problem. It was out of alighment/bent and thus knocking. It was loud and worrying when cold starting. When the car was driven for a while and hot the knocking noise was much less apparent but could just hear it. 

 

Having initially thought it might be the cambelt pulley , when i had this changed yesterday the mechanic identified the aux belt issue and i had the belt/pulley/tensioner replaced and the knocking has completely disappeared.